#
Relationships Between Amino Acid Sequence and Backbone Torsion
Angle Preferences

**Ozlem Keskin, Deniz Yuret, Attila Gursoy, Metin Turkay, Burak
Erman (2004)**
(PDF)
- Relationships Between Amino Acid Sequence
and Backbone Torsion Angle Preferences.
*Proteins:
Structure, Function, and Bioinformatics.* 55(4):992-8.

### Abstract:

Statistical averages and correlations for backbone torsion angles of
chymotrypsin inhibitor 2 are calculated by using the Rotational
Isomeric States model of chain statistics. Statistical weights of
torsional states of phi-psi pairs, needed for the statistics of the
full chain, are obtained in two different ways: 1) by using
knowledge-based pairwise dependent phi-psi energy maps from Protein
Data Bank (PDB) and 2) by collecting torsion angle data from a large
number of random coil configurations of an all-atom protein model with
volume exclusion. Results obtained by using PDB data show strong
correlations between adjacent torsion angle pairs belonging to both
the same and different residues. These correlations favor the choice
of the nativestate torsion angles, and they are strongly context
dependent, determined by the specific amino acid sequence of the
protein. Excluded volume or steric clashes, only, do not introduce
context-dependent phi-psi correlations into the chain that would
affect the choice of native-state torsional angles.